Video-frame data receiver with low frame capture rate

ABSTRACT

The present disclosure relates generally to a video frame data receiver that is capable of image acquisition at low frame rates. Such video frame data receivers may be used to capture images from diagnostic tests or assays in which lower frame capture rates are sufficient including, for example, lateral flow test strips.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/231,169, filed Mar. 31, 2014 and scheduled to issue on Dec. 15, 2015as U.S. Pat. No. 9,215,351, which is a divisional of U.S. applicationSer. No. 12/354,134, filed Jan. 15, 2009 and issued as U.S. Pat. No.8,692,873 on Apr. 8, 2014. The disclosures of all of theabove-referenced prior applications, publications, and patents areconsidered part of the disclosure of this application, and areincorporated by reference herein in their entirety.

BACKGROUND

Assay test kits currently are available for testing a wide variety ofmedical and environmental conditions or compounds, such as a hormone, ametabolite, a toxin, or a pathogen-derived antigen. Most commonly thesetests are used for medical diagnostics either for home testing, point ofcare testing, or laboratory use. For example, lateral flow tests are aform of immunoassay in which the test sample flows along a solidsubstrate via capillary action. Some tests are designed to make aquantitative determination, but in many circumstances all that isrequired is a positive/negative qualitative indication. Examples of suchqualitative assays include blood typing, most types of urinalysis,pregnancy tests, and AIDS tests. For these tests, a visually observableindicator such as the presence of agglutination or a color change ispreferred.

Readers for assays including, for example, lateral flow assays may use acamera for acquisition of images from the assay for subsequentprocessing and analysis. These readers may require an interface betweenthe camera and a microcontroller that accesses images from the camerafor subsequent processing and analysis. Conventional solutions ofmicrocontroller-camera interfaces deploy a FGPA, a CPLD or a FIFO as theglue logic between the microcontroller and camera. The purpose of suchglue logic is to stream images into a frame buffer located in itsinternal or external memory. The microcontroller can then access theimage data inside the frame buffer for transmission or furtherprocessing.

SUMMARY

The present disclosure provides a video frame data receiver that iscapable of image acquisition from a camera or other type of image sensorat low frame rates. Such video frame data receivers may be used tocapture images indicative of the progress of diagnostic tests or assaysin which slow frame capture rates are sufficient including, for example,lateral flow test strips.

The present disclosure relates to video frame data receivers thatcomprise at least one microprocessor; at least one signal receiver; andat least one memory device, wherein the at least one memory devicestores instructions which, when executed by the at least onemicroprocessor, cause the at least one microprocessor to operate withthe at least one signal receiver to: receive a first synchronizingsignal from an image sensor in signal communication with said at leastone microprocessor, said image sensor configured to store dataindicative of a video frame, said first synchronizing signal indicatingwhether the image sensor is storing data indicative of an end of a videoframe. In an embodiment, the first synchronizing signal (such as a vsyncsignal) is active for the duration of a capture of a video frame by animage sensor. That is, by sensing that the first synchronizing signal isactive, the In a further embodiment, the instructions cause the at leastone microprocessor to operate with the at least one signal receiver toreceive a second synchronizing signal from the image sensor, said secondsynchronizing signal indicating whether the image sensor is storing dataindicative of an end of one of a plurality of lines of the video frame.In an embodiment, the second synchronizing signal (such as an hsyncsignal) is active for the duration of a capture of a line of a videoframe by an image sensor. In one embodiment, the instructions also causethe at least one microprocessor to operate with the at least one signalreceiver to receive a clock signal from the image sensor, said clocksignal indicating whether said image sensor is currently storing validdata indicative of at least a portion of the video frame, at a firstpoint in time, determine whether said first synchronizing signalindicates that the image sensor is storing data indicative of the end ofat least the portion of the video frame, at said first point in time,also determine whether said second synchronizing signal indicates thatthe image sensor is storing data indicative of the end of one of theplurality of lines of the video frame. For example, the microprocessormay determine whether both the first synchronizing signal and the secondsynchronizing signal are both active at the first point in time. If, atthe first point in time, the first synchronizing signal indicates thatthe image sensor is storing data indicative of the end of the videoframe and the second synchronizing signal simultaneously indicates thatthe image sensor is storing data indicative of the end of one of theplurality of lines of the video frame (that is, the synchronizingsignals are each active, indicating that the end of a last line of avideo frame has been captured), the instructions cause themicroprocessor to operate with the at least one signal receiver to pollthe clock signal until said clock signal indicates that said imagesensor is currently storing valid data indicative of at least a portionof the video frame, and when the clock signal indicates that the imagesensor is currently storing valid data indicative of at least a portionof the video frame, to read and store the then-stored data indicative ofat least the portion of the video frame from the image sensor.

In an embodiment, the image sensor operates asynchronously with respectto the at least one microprocessor. For example, the image sensor mayoperate asynchronously with respect to the at least one microprocessorbecause the image sensor is in signal communication with an externaloscillator. In another embodiment, the image sensor operatesasynchronously with respect to the at least one microprocessor due to anexternal crystal. In an embodiment, the image sensor operatessynchronously with respect to the at least one microprocessor byutilizing a same clock signal generator as the at least onemicroprocessor.

In an embodiment, the same clock signal generator is afrequency-division circuit which is in signal communication with the atleast one microprocessor and the image sensor. In further embodiments,the frequency-division circuit is realized by or implemented as apulse-width modulator or a programmable clock peripheral.

In an embodiment, the instructions cause the at least one microprocessorto poll the clock signal until said clock signal indicates that saidimage sensor is currently storing valid data indicative of at least aportion of the video frame by polling the clock signal until detectingat least one selected from the group consisting of a rising edge of saidclock signal and falling edge of said clock signal.

In an embodiment, the video frame data receiver of the presentdisclosure further comprises a general purpose input/output peripheral,and the instructions cause the at least one microprocessor to operatewith the general purpose input/output peripheral to read and store thethen-stored data indicative of at least the portion of the video framefrom the image sensor.

In an embodiment, the video frame data receiver of the presentdisclosure further comprises an external memory interface, and theinstructions cause the at least one microprocessor to operate with theexternal memory interface to read and store the then-stored dataindicative of at least the portion of the video frame from the imagesensor. In an embodiment, the external memory interface is a separatepackage from the printed circuit board containing the microprocessor. Inanother embodiment, the external memory interface is included in a samepackage or on a same printed circuit board as the microprocessor—forexample, the external memory interface may include an interface toon-chip memory. In certain embodiments, the external memory storesmicroprocessor instructions for execution by the at least onemicroprocessor in addition to (or instead of) storing the video framedata from the image sensor.

In an embodiment, the external memory interface enables the at least onemicroprocessor to communicate with at least one type of external memoryunit selected from the group consisting of: a read only memory (ROM)unit, a flash memory unit, and a static random access memory (SRAM)unit. In one embodiment, wherein the external memory interface enablesthe at least one microprocessor to communicate with an external readonly memory (ROM) unit, it should be appreciated that the external ROMunit may not be configured to store data indicative of at least aportion of a video frame. Rather, the external ROM unit may store onlyinstructions for execution by the at least one microprocessor.

The present disclosure also relates to or provides video frame datareceivers that comprise at least one microprocessor; at least one signalreceiver; and at least one memory device, wherein the at least onememory device stores instructions which, when executed by the at leastone microprocessor, cause the at least one microprocessor to operatewith the at least one signal receiver to: receive a first synchronizingsignal from an image sensor, such as a camera, in signal communicationwith said at least one microprocessor, said image sensor configured tostore data indicative of a video frame, said first synchronizing signalindicating whether the image sensor is storing data indicative of an endof a video frame. In an embodiment, the first synchronizing signal (suchas a vsync signal) is active for the duration of a capture of a videoframe by an image sensor. In a further embodiment, the instructionscause the at least one microprocessor to operate with the at least onesignal receiver to receive a second synchronizing signal from the imagesensor, said second synchronizing signal indicating whether the imagesensor is storing data indicative of an end of one of a plurality oflines of the video frame. In an embodiment, the second synchronizingsignal (such as an hsync signal) is active for the duration of a captureof a line of a video frame by an image sensor. In one embodiment, theinstructions also cause the at least one microprocessor to operate withthe at least one signal receiver to receive a clock signal from theimage sensor, said clock signal indicating whether said image sensor iscurrently storing valid data indicative of at least a portion of thevideo frame, detect an interrupt based on said clock signal, saidinterrupt indicating that said image sensor is currently storing validdata indicative of at least a portion of the video frame, upon detectionof said interrupt, determine whether said first synchronizing signalindicates that the image sensor is storing data indicative of the end ofthe video frame and determine whether said second synchronizing signalindicates that the image sensor is storing data indicative of the end ofone of the plurality of lines of the video frame. If, upon detection ofthe interrupt, the first synchronizing signal indicates that the imagesensor is storing data indicative of the end of the video frame and thesecond synchronizing signal indicates that the image sensor is storingdata indicative of the end of one of the plurality of lines of the videoframe (that is, the synchronizing signals together indicate that the endof a last line of a video frame has been captured), the instructionscause the microprocessor to operate with the at least one signalreceiver to read and store the then-stored data indicative of the videoframe from the image sensor.

In an embodiment, the image sensor operates asynchronously with respectto the at least one microprocessor. For example, the image sensor mayoperate asynchronously with respect to the at least one microprocessorbecause the image sensor is in signal communication with an externaloscillator. Alternatively, the image sensor operates asynchronously withrespect to the at least one microprocessor due to the presence of anexternal crystal.

In an embodiment, the image sensor operates synchronously with respectto the at least one microprocessor by utilizing a same clock signalgenerator as the at least one microprocessor. In a further embodiment,the same clock signal generator is frequency-division circuit in signalcommunication with the at least one microprocessor and the image sensor.In further embodiments, the frequency-division circuit is realized by orimplemented as a pulse-width modulator or a programmable clockperipheral which is in signal communication with the at least onemicroprocessor and the image sensor.

In an embodiment, the instructions cause the at least one microprocessorto detect an interrupt based on said clock signal by determining atleast one selected from the group consisting of a rising edge and afalling edge of said clock signal.

In an embodiment, the video frame data receiver of the presentdisclosure further comprises a general purpose input/output peripheral,and wherein the instructions cause the at least one microprocessor tooperate with the general purpose input/output peripheral to read andstore the then-stored data indicative of at least the portion of thevideo frame from the image sensor.

In an embodiment, the video frame data receiver of the presentdisclosure further comprises an external memory interface, and whereinthe instructions cause the at least one microprocessor to operate withthe external memory interface to read and store the then-stored dataindicative of either or both of at least the portion of the video framefrom the image sensor or instructions for execution by the at least onemicroprocessor. In one embodiment, the external memory interface is aseparate package from the printed circuit board containing themicroprocessor. In another embodiment, the external memory interface isincluded in a same package or on a same printed circuit board as themicroprocessor—for example, the external memory interface may include aninterface to on-chip memory. In certain embodiments, the external memorystores microprocessor instructions for execution by the at least onemicroprocessor in addition to (or instead of) storing the video framedata from the image sensor.

In an embodiment, the external memory interface enables the at least onemicroprocessor to communicate with at least one type of external memoryunit selected from the group consisting of: a read only memory (ROM)unit, a flash memory unit, and a static random access memory (SRAM)unit, as discussed above. In one embodiment, wherein the external memoryinterface enables the at least one microprocessor to communicate with anexternal read only memory (ROM) unit, it should be appreciated that theexternal ROM unit may not be configured to store data indicative of atleast a portion of a video frame. Rather, the external ROM unit maystore only instructions for execution by the at least onemicroprocessor.

The present disclosure also provides a video frame data receiver thatcomprises at least one microprocessor; at least one signal receiver; andat least one memory device, wherein the at least one memory devicestores instructions which, when executed by the at least onemicroprocessor, cause the at least one microprocessor to operate withthe at least one signal receiver to: receive a first synchronizingsignal from the image sensor, said first synchronizing signal indicatingwhether the image sensor is storing data indicative of an end of one ofa plurality of lines of the video frame. In an embodiment, the firstsynchronizing signal (such as an hsync signal) is active for theduration of a capture of a line of a video frame by an image sensor. Inone embodiment, the instructions also cause the at least onemicroprocessor to operate with the at least one signal receiver toreceive a clock signal from the image sensor, said clock signalindicating whether said image sensor is currently storing valid dataindicative of at least a portion of the video frame, detect an interruptbased on said first synchronizing signal, said interrupt indicating thatsaid image sensor is storing data indicative of the end of one of theplurality of lines of the video frame, and upon detection of saidinterrupt: determine whether the image sensor is currently storing validdata indicative of at least the portion of the video frame (that is,determine whether the first synchronizing signal indicates the end of alast line of a video frame has been captured). If so, the instructionscause the microprocessor to operate with the at least one signalreceiver to read and store the then-stored data indicative of at leastthe portion of the video frame from the image sensor.

In an embodiment, the image sensor operates asynchronously with respectto the at least one microprocessor because the image sensor is in signalcommunication with an external oscillator.

In an embodiment, the image sensor operates synchronously with respectto the at least one microprocessor by utilizing a same clock signalgenerator as the at least one microprocessor. In one such embodiment,the same clock signal generator is a frequency-division circuit which isin signal communication with the at least one microprocessor and theimage sensor. In further embodiments, the frequency-division circuit isrealized by or implemented as a pulse-width modulator or a programmableclock peripheral in signal communication with the at least onemicroprocessor and the image sensor.

In an embodiment, the instructions cause the at least one microprocessorto detect an interrupt based on said first synchronizing signal bydetecting at least one feature of the first synchronizing signal. Forexample, the microprocessor may detect an interrupt by detecting arising edge of said first synchronizing signal or a falling edge of saidfirst synchronizing signal.

In an embodiment, the video frame data receiver of the presentdisclosure further comprises a general purpose input/output peripheral,and wherein the instructions cause the at least one microprocessor tooperate with the general purpose input/output peripheral to read andstore the then-stored data indicative of at least the portion of thevideo frame from the image sensor.

In an embodiment, the instructions cause the at least one microprocessorto determine whether the image sensor is currently storing valid dataindicative of at least the portion of the video frame by polling theclock signal to determine a feature of the clock signal. For example,the microprocessor may poll the clock signal to determine a data-validedge of said clock signal. In various embodiments, the data-valid edgeof the clock signal is either a rising edge of said clock signal or afalling edge of said clock signal. In an embodiment, the instructionscause the at least one microprocessor to determine whether the imagesensor is currently storing valid data indicative of the video framebased on whether the clock signal is currently in a data-validhalf-period.

In an embodiment, upon determining that the image sensor is currentlystoring valid data indicative of the video frame (such as by detecting arising edge of the clock signal or a falling edge of the clock signal),the instructions cause the at least one microprocessor to read and storethe then-stored data indicative of the video frame from the image sensorwithin a time period equal to less than one-half of the period of theclock signal. In another embodiment, the instructions cause the at leastone microprocessor to read the data indicative of the video frame withina time period equal to less than one-half of the period of the clocksignal, but storage of that data occurs within a time period exceedingone-half of the period of the clock signal. For example, the disclosedsystem may read and store the data within an entire clock period. Itshould be appreciated that any suitable timing for reading and storingmay be used in various embodiments.

In an embodiment, if the image sensor is currently storing valid dataindicative of the video frame, the instructions cause the at least onemicroprocessor to read the then-stored data indicative of the videoframe only during the current data-valid half-period. The microprocessormay store the data indicative of the portion of the video frame during aperiod outside of the data-valid half period. For example, the at leastone microprocessor may both read and store the then-stored dataindicative of the video frame during an entire clock period.

The present disclosure also provides video frame data receivers thatcomprise at least one microprocessor; at least one signal receiver; andat least one memory device, wherein the at least one memory devicestores instructions which, when executed by the at least onemicroprocessor, cause the at least one microprocessor to operate withthe at least one signal receiver to: receive a first synchronizingsignal from the image sensor, said first synchronizing signal indicatingwhether the image sensor is storing data indicative of an end of one ofa plurality of lines of the video frame. For example, the firstsynchronizing signal may be a hsync signal as discussed above. In oneembodiment, the microprocessor is also programmed to receive a clocksignal from the image sensor, said clock signal indicating whether saidimage sensor is currently storing valid data indicative of at least aportion of the video frame. In one embodiment, the microprocessordetects an interrupt based on said first synchronizing signal, saidinterrupt indicating that said image sensor is storing data indicativeof the end of one of the plurality of lines of the video frame, and upondetection of said interrupt, reads and stores the then-stored dataindicative of at least the portion of the video frame from the imagesensor only during the current data-valid half-period due to analignment of said execution of said instructions with said clock signal.In a further embodiment, the microprocessor reads the data indicative ofthe portion of the video frame during the data-valid half period, andstores the data during a longer period, such as an entire clock period.

The present disclosure also provides a diagnostic test reader comprisingan image sensor for capturing an image of a diagnostic test, said imageindicating an outcome of the diagnostic test. In one embodiment, saiddiagnostic test is an assay test strip. In such an embodiment, the imagemay indicate the outcome of the diagnostic test by indicating an amountof lateral flow of an assay along said assay test strip. In oneembodiment, the diagnostic test reader includes at least onemicroprocessor; at least one signal receiver; and at least one memorydevice, wherein the at least one memory device stores instructionswhich, when executed by the at least one microprocessor, cause the atleast one microprocessor to operate with the at least one signalreceiver and the at least one image sensor to: receive a firstsynchronizing signal (such as the hsync signals discussed above) from animage sensor in signal communication with said at least onemicroprocessor, said image sensor configured to store data indicative ofa video frame representing said image, said first synchronizing signalindicating whether the image sensor is storing data indicative of an endof one of a plurality of lines of a video frame representing said image.The microprocessor is additionally configured to receive a clock signalfrom the image sensor, said clock signal indicating whether said imagesensor is currently storing valid data indicative of at least a portionof the video frame. For example, the detecting a feature of the clocksignal (such as rising or falling edge of the clock signal) may indicatethat the image sensor is currently storing valid data. Themicroprocessor is also configured to detect an interrupt based on saidfirst synchronizing signal, said interrupt indicating that said imagesensor is storing data indicative of the end of one of the plurality oflines of the video frame, and upon detection of said interrupt:determine whether the image sensor is currently storing valid dataindicative of at least the portion of the video frame (such as based onthe clock signal). If the microprocessor determines that the imagesensor is currently storing valid data indicative of at least theportion of the video frame, the microprocessor is configured to read andstore the then-stored data indicative of at least the portion of thevideo frame from the image sensor.

In an embodiment, upon determining that the image sensor is currentlystoring valid data indicative of the video frame, the instructions causethe at least one microprocessor to read and store the then-stored dataindicative of the video frame from the image sensor within a time periodequal to less than one-half of the period of the clock signal. In afurther embodiment, the microprocessor does not need to store the dataindicative of at least a portion of the video frame within one-half of aclock period. In this embodiment, the microprocessor can read the dataindicative of at least a portion of the video frame within the one-halfclock period, and can read and store the data within a full clockperiod. In another embodiment, the microprocessor is programmed to bothread and store the data indicative of at least the portion of the videoframe within one-half of a clock period.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of the microcontroller-camera interface.

FIG. 2 is a flow diagram illustrating the steps performed by amicrocontroller in one embodiment of the system disclosed herein.

DETAILED DESCRIPTION

The present disclosure provides video frame data receivers that arecapable of image acquisition at low frame rates. While conventionalvideo frame data receivers are capable of real-time video capture (e.g.,15 to 30 frame per second), they are inefficient for applications inwhich lower frame capture rates are desired. The video frame datareceivers of the present disclosure may be used to capture images fromdiagnostic test or assays in which lower frame capture rates (e.g.,approximately 5 frames per second or less) are desired including, forexample, lateral flow test strips. The video frame data receivers of thepresent disclosure remove the need for a glue logic comprised ofdiscrete components and lends itself to a wide range of microprocessorsand microcontrollers lacking dedicated hardware camera interfaces.Accordingly, additional electronic components beyond the microcontrollerand camera module are not necessary since the task of interfacing thecamera and microcontroller is performed by the microcontroller'sfirmware.

The video frame data receivers of the present disclosure are preferablyused with an immunoassay device including, for example, devices used tomeasure one or more analytes on an assay.

Exemplary assays contemplated for use with the methods of the presentdisclosure include lateral flow assay test strips. Lateral flow assaytest strips may comprise a membrane system that forms a single fluidflow pathway along the test strip. The membrane system may include oneor more components that act as a solid support for immunoreactions. Forexample, porous, bibulous or absorbent materials may be placed on astrip such that they partially overlap, or a single material can beused, in order to conduct liquid along the strip. The membrane materialsmay be supported on a backing, such as a plastic backing. In a preferredembodiment, the test strip includes a glass fiber pad, a nitrocellulosestrip and an absorbent cellulose paper strip supported on a plasticbacking.

Antibodies that react with the target analyte and/or a detectable labelsystem are immobilized on the solid support. The antibodies may be boundto the test strip by adsorption, ionic binding, van der Waalsadsorption, electrostatic binding, or by covalent binding, by using acoupling agent, such as glutaraldehyde. For example, the antibodies maybe applied to the conjugate pad and nitrocellulose strip using standarddispensing methods, such as a syringe pump, air brush, ceramic pistonpump or drop-on-demand dispenser. In a preferred embodiment, avolumetric ceramic piston pump dispenser may be used to stripeantibodies that bind the analyte of interest, including a labeledantibody conjugate, onto a glass fiber conjugate pad and anitrocellulose strip. The test strip may or may not be otherwisetreated, for example, with sugar to facilitate mobility along the teststrip or with water-soluble non-immune animal proteins, such asalbumins, including bovine (BSA), other animal proteins, water-solublepolyamino acids, or casein to block non-specific binding sites.

Any antibody, including polyclonal or monoclonal antibodies, or anyfragment thereof, such as the Fab fragment, that binds the analyte ofinterest, is contemplated for use herein.

An antibody conjugate containing a detectable label may be used to bindthe analyte of interest. The detectable label used in the antibodyconjugate may be any physical or chemical label capable of beingdetected on a solid support using a reader, preferably a reflectancereader, and capable of being used to distinguish the reagents to bedetected from other compounds and materials in the assay.

Suitable antibody labels are well known to those of skill in the art andinclude, but are not limited to, enzyme-substrate combinations thatproduce color upon reaction, colored particles, such as latex particles,colloidal metal or metal or carbon sol labels, fluorescent labels, andliposome or polymer sacs, which are detected due to aggregation of thelabel. In an embodiment, colloidal gold is used in the labeled antibodyconjugate. The label may be derivatized for linking antibodies, such asby attaching functional groups, such as carboxyl groups to the surfaceof a particle to permit covalent attachment of antibodies. Antibodiesmay be conjugated to the label using well known coupling methods.

The assay test strip may be any conventional lateral flow assay teststrip such as disclosed in EP 291194 or U.S. Pat. No. 6,352,862. Thetest strip may comprise a porous carrier containing a particulatelabeled specific binding reagent and an unlabelled specific bindingreagent. The light sources and corresponding photodetectors arepreferably so aligned such that during use, light from the light sourceor sources falls upon the respective zones on the porous carrier and isreflected or transmitted to the respective photodetectors. Thephotodetectors may then generate a current roughly proportional to theamount of light falling upon it. The amount of light reaching thephotodetector depends upon the amount of colored particulate labelpresent and therefore the amount of analyte. Thus the amount of analytepresent in the sample may be determined. This method of opticallydetermining the analyte concentration is described more fully in EP653625.

A sample may include, for example, anything which may contain an analyteof interest. The sample may be a biological sample, such as a biologicalfluid or a biological tissue. Examples of biological fluids includeurine, blood, plasma, serum, saliva, semen, stool, sputum, cerebralspinal fluid, tears, mucus, amniotic fluid or the like. Biologicaltissues are aggregate of cells, usually of a particular kind togetherwith their intercellular substance that form one of the structuralmaterials of a human, animal, plant, bacterial, fungal or viralstructure, including connective, epithelium, muscle and nerve tissues.Examples of biological tissues also include organs, tumors, lymph nodes,arteries and individual cells.

A fluid sample (e.g., biological fluid) may refer to a materialsuspected of containing the analyte(s) of interest, which material hassufficient fluidity to flow through an immunoassay device in accordanceherewith. The fluid sample can be used as obtained directly from thesource or following a pretreatment so as to modify its character. Suchsamples can include human, animal or man-made samples. The sample can beprepared in any convenient medium which does not interfere with theassay.

The fluid sample can be derived from any source, such as a physiologicalfluid, including blood, serum, plasma, saliva, sputum, ocular lensfluid, sweat, urine, milk, ascites fluid, mucous, synovial fluid,peritoneal fluid, transdermal exudates, pharyngeal exudates,bronchoalveolar lavage, tracheal aspirations, cerebrospinal fluid,semen, cervical mucus, vaginal or urethral secretions, amniotic fluid,and the like. Herein, fluid homogenates of cellular tissues such as, forexample, hair, skin and nail scrapings, meat extracts and skins offruits and nuts are also considered biological fluids. Pretreatment mayinvolve preparing plasma from blood, diluting viscous fluids, and thelike. Methods of treatment can involve filtration, distillation,separation, concentration, inactivation of interfering components, andthe addition of reagents. Besides physiological fluids, other samplescan be used such as water, food products, soil extracts, and the likefor the performance of industrial, environmental, or food productionassays as well as diagnostic assays. In addition, a solid materialsuspected of containing the analyte can be used as the test sample onceit is modified to form a liquid medium or to release the analyte.

Exemplary lateral flow devices include those described in U.S. Pat. Nos.4,818,677, 4,943,522, 5,096,837 (RE 35,306), 5,096,837, 5,118,428,5,118,630, 5,221,616, 5,223,220, 5,225,328, 5,415,994, 5,434,057,5,521,102, 5,536,646, 5,541,069, 5,686,315, 5,763,262, 5,766,961,5,770,460, 5,773,234, 5,786,220, 5,804,452, 5,814,455, 5,939,331,6,306,642.

A sample may include, for example, anything which may contain ananalyte. The sample may be a biological sample, such as a biologicalfluid or a biological tissue. Examples of biological fluids includeurine, blood, plasma, serum, saliva, semen, stool, sputum, cerebralspinal fluid, tears, mucus, amniotic fluid or the like. Biologicaltissues are aggregate of cells, usually of a particular kind togetherwith their intercellular substance that form one of the structuralmaterials of a human, animal, plant, bacterial, fungal or viralstructure, including connective, epithelium, muscle and nerve tissues.Examples of biological tissues also include organs, tumors, lymph nodes,arteries and individual cell(s). A liquid sample may refer to a materialsuspected of containing the analyte(s) of interest, which material hassufficient fluidity to flow through an immunoassay device in accordanceherewith. The fluid sample can be used as obtained directly from thesource or following a pretreatment so as to modify its character. Suchsamples can include human, animal or man-made samples. The sample can beprepared in any convenient medium which does not interfere with theassay. Typically, the sample is an aqueous solution or biological fluidas described in more detail below.

The fluid sample can be derived from any source, such as a physiologicalfluid, including blood, serum, plasma, saliva, sputum, ocular lensfluid, sweat, urine, milk, ascites fluid, mucous, synovial fluid,peritoneal fluid, transdermal exudates, pharyngeal exudates,bronchoalveolar lavage, tracheal aspirations, cerebrospinal fluid,semen, cervical mucus, vaginal or urethral secretions, amniotic fluid,and the like. Herein, fluid homogenates of cellular tissues such as, forexample, hair, skin and nail scrapings, meat extracts and skins offruits and nuts are also considered biological fluids. Pretreatment mayinvolve preparing plasma from blood, diluting viscous fluids, and thelike. Methods of treatment can involve filtration, distillation,separation, concentration, inactivation of interfering components, andthe addition of reagents. Besides physiological fluids, other samplescan be used such as water, food products, soil extracts, and the likefor the performance of industrial, environmental, or food productionassays as well as diagnostic assays. In addition, a solid materialsuspected of containing the analyte can be used as the test sample onceit is modified to form a liquid medium or to release the analyte.

An analyte can be any substance for which there exists a naturallyoccurring analyte specific binding member or for which ananalyte-specific binding member can be prepared. e.g., carbohydrate andlectin, hormone and receptor, complementary nucleic acids, and the like.Further, possible analytes include virtually any compound, composition,aggregation, or other substance which may be immunologically detected.That is, the analyte, or portion thereof, will be antigenic or haptenichaving at least one determinant site, or will be a member of a naturallyoccurring binding pair.

Analytes include, but are not limited to, toxins, organic compounds,proteins, peptides, microorganisms, bacteria, viruses, amino acids,nucleic acids, carbohydrates, hormones, steroids, vitamins, drugs(including those administered for therapeutic purposes as well as thoseadministered for illicit purposes), pollutants, pesticides, andmetabolites of or antibodies to any of the above substances. The termanalyte also includes any antigenic substances, haptens, antibodies,macromolecules, and combinations thereof (see, e.g., U.S. Pat. Nos.4,366,241; 4,299,916; 4,275,149; and 4,806,311).

In an embodiment, a sample receiving zone on the surface of a lateralflow assay test strip accepts a fluid sample that may contain one ormore analytes of interest. In an embodiment, the sample receiving zoneis dipped into a fluid sample. A label zone is located downstream of thesample receiving zone, and contains one or more mobile label reagentsthat recognize, or are capable of binding the analytes of interest.Further, a test region may be disposed downstream from the label zone,and contains test and control zones. The test zone(s) generally containmeans which permit the restraint of a particular analyte of interest ineach test zone. Frequently, the means included in the test zone(s)comprise an immobilized capture reagent that binds to the analyte ofinterest. Generally the immobilized capture reagent specifically bindsto the analyte of interest. Thus, as the fluid sample flows along thematrix, the analyte of interest will first bind with a mobilizable labelreagent in the label zone, and then become restrained in the test zone.

In an embodiment, the sample receiving zone may be comprised of anabsorbent application pad. Suitable materials for manufacturingabsorbent application pads include, but are not limited to, hydrophilicpolyethylene materials or pads, acrylic fiber, glass fiber, filter paperor pads, desiccated paper, paper pulp, fabric, and the like. Forexample, the sample receiving zone may be comprised of a material suchas a nonwoven spunlaced acrylic fiber.

The sample receiving zone may be comprised of any material from whichthe fluid sample can pass to the label zone. Further, the absorbentapplication pad can be constructed to act as a filter for cellularcomponents, hormones, particulate, and other certain substances that mayoccur in the fluid sample. Application pad materials suitable for use bythe present invention also include those application pad materialsdisclosed in U.S. Pat. No. 5,075,078.

In a further embodiment, the sample receiving zone may be comprised ofan additional sample application member (e.g., a wick). Thus, in oneaspect, the sample receiving zone can comprise a sample application padas well as a sample application member. Often the sample applicationmember is comprised of a material that readily absorbs any of a varietyof fluid samples contemplated herein, and remains robust in physicalform. Frequently, the sample application member is comprised of amaterial such as white bonded polyester fiber. Moreover, the sampleapplication member, if present, is positioned in fluid-flow contact witha sample application pad.

In an embodiment, the label zone material may be treated with labeledsolution that includes material-blocking and label-stabilizing agents.Blocking agents include, for example, bovine serum albumin (BSA),methylated BSA, casein and nonfat dry milk. Stabilizing agents arereadily available and well known in the art, and may be used, forexample, to stabilize labeled reagents.

The label zone may contain a labeled reagent, often comprising one ormore labeled reagents. In many of the presently contemplatedembodiments, multiple types of labeled reagents are incorporated in thelabel zone such that they may permeate together with a fluid samplecontacted with the device. These multiple types of labeled reagent canbe analyte specific or control reagents and may have differentdetectable characteristics (e.g., different colors) such that onelabeled reagent can be differentiated from another labeled reagent ifutilized in the same device. As the labeled reagents are frequentlybound to a specific analyte of interest subsequent to fluid sample flowthrough the label zone, differential detection of labeled reagentshaving different specificities (including analyte specific and controllabeled reagents) may be a desirable attribute. However, frequently, theability to differentially detect the labeled reagents having differentspecificities based on the label component alone is not necessary due tothe presence of test and control zones in the device, which allow forthe accumulation of labeled reagent in designated zones.

The labeling zone may also include control-type reagents. These labeledcontrol reagents often comprise detectible moieties that will not becomerestrained in the test zones and that are carried through to the testregion and control zone(s) by fluid sample flow through the device. In afrequent embodiment, these detectible moieties are coupled to a memberof a specific binding pair to form a control conjugate which can then berestrained in a separate control zone of the test region by acorresponding member of the specific binding pair to verify that theflow of liquid is as expected. The visible moieties used in the labeledcontrol reagents may be the same or different color, or of the same ordifferent type, as those used in the analyte of interest specificlabeled reagents. If different colors are used, ease of observing theresults may be enhanced.

The test region may include a control zone for verification that thesample flow is as expected. Each of the control zones comprise aspatially distinct region that often includes an immobilized member of aspecific binding pair which reacts with a labeled control reagent. In anoccasional embodiment, the procedural control zone contains an authenticsample of the analyte of interest, or a fragment thereof. In thisembodiment, one type of labeled reagent can be utilized, wherein fluidsample transports the labeled reagent to the test and control zones; andthe labeled reagent not bound to an analyte of interest will then bindto the authentic sample of the analyte of interest positioned in thecontrol zone. In another embodiment, the control line contains antibodythat is specific for, or otherwise provides for the immobilization of,the labeled reagent. In operation, a labeled reagent is restrained ineach of the one or more control zones, even when any or all the analytesof interest are absent from the test sample.

Since the devices of the present invention may incorporate one or morecontrol zones, the labeled control reagent and their correspondingcontrol zones are preferably developed such that each control zone willbecome visible with a desired intensity for all control zones afterfluid sample is contacted with the device, regardless of the presence orabsence of one or more analytes of interest. In one embodiment, a singlelabeled control reagent will be captured by each of the control zones onthe test strip. Frequently, such a labeled control reagent will bedeposited onto or in the label zone in an amount exceeding the capacityof the total binding capacity of the combined control zones if multiplecontrol zones are present. Accordingly, the amount of capture reagentspecific for the control label can be deposited in an amount that allowsfor the generation of desired signal intensity in the one or morecontrol zones, and allows each of the control zones to restrain adesired amount of labeled control-reagent. At the completion of anassay, each of the control zones preferably provide a desired and/orpre-designed signal (in intensity and form).

In an embodiment, each control zone will be specific for a uniquecontrol reagent. In this embodiment, the label zone may include multipleand different labeled control reagents, equaling the number of controlzones in the assay, or a related variation. Wherein each of the labeledcontrol reagents may become restrained in one or more predetermined andspecific control zone(s). These labeled control reagents can provide thesame detectible signal (e.g., be of the same color) or providedistinguishable detectible signals (e.g., have different colored labelsor other detection systems) upon accumulation in the control zone(s).

In an embodiment, the labeled control reagent comprises a detectiblemoiety coupled to a member of a specific binding pair. Typically, alabeled control reagent is chosen to be different from the reagent thatis recognized by the means which are capable of restraining an analyteof interest in the test zone. Further, the labeled control reagent isgenerally not specific for the analyte. In a frequent embodiment, thelabeled control reagent is capable of binding the corresponding memberof a specific binding pair or control capture partner that isimmobilized on or in the control zone. Thus the labeled control reagentis directly restrained in the control zone.

The use of a control zone is helpful in that appearance of a signal inthe control zone indicates the time at which the test result can beread, even for a negative result. Thus, when the expected signal appearsin the control line, the presence or absence of a signal in a test zonecan be noted.

Test zones of the present description include means that permit therestraint of an analyte of interest. Frequently, test zones of thepresent description include a ligand that is capable of specificallybinding to an analyte of interest. Alternatively, test zones of thepresent description include a ligand that is capable of specificallybinding the labeled reagent bound to an analyte of interest. Inpractice, a labeled test reagent binds an analyte of interest present ina fluid sample after contact of the sample with a representative deviceand flow of the fluid sample into and through the label zone.Thereafter, the fluid sample containing the labeled analyte progressesto a test zone and becomes restrained in the test zone. The accumulationof labeled analyte in the test zone produces a detectible signal.Devices may incorporate one or more test zones, each of which is capableof restraining different analytes, if present, in a fluid sample. Thus,in representative embodiments two, three, four, five or more (labeled)analytes of interest can be restrained in a single or different testzones, and thereby detected, in a single device.

The present devices may optionally further comprise an absorbent zonethat acts to absorb excess sample after the sample migrates through thetest region. The absorbent zone, when present lies in fluid flow contactwith the test region. This fluid flow contact can comprise anoverlapping, abutting or interlaced type of contact. In an occasionalembodiment, a control region (end of assay indicator) is provided in theabsorbent zone to indicate when the assay is complete. In thisembodiment, specialized reagents are utilized, such as pH sensitivereagents (such as bromocresol green), to indicate when the fluid samplehas permeated past all of the test and control zones.

The test strip optionally may be contained within a housing forinsertion into the reflectance reader. The housing may be made ofplastic or other inert material that does not interfere with the assayprocedure.

The lateral flow assay test strip may be suited for use with a readingdevice that comprises one or more of the following: a central processingunit (CPU) or microcontroller; one, two, or more LED's; one, two, ormore photodiodes; a power source; and associated electrical circuitry.The power source may comprise a battery or any other suitable powersource (e.g. a photovoltaic cell). The CPU will typically be programmedso as to determine whether the calculated rate and/or extent of progressof the liquid sample is within predetermined limits.

Conveniently the assay result reading device will comprise some mannerof indicating the result of the assay to a user. This may take the form,for example, of an audible or visible signal. Desirably the device willcomprise a visual display to display the assay result. This may simplytake the form of one or more LED's or other light sources, such thatillumination of a particular light source or combination of lightsources conveys the necessary information to the user. Alternatively thedevice may be provided with an alphanumeric or other display, such as anLCD. In addition, or as an alternative, to displaying the assay result,the device may also display or indicate in some other way to the userwhether the calculated rate and/or extent of progress of the liquidsample is within the predetermined acceptable limits, and thus whetheror not the result of the particular assay should be disregarded. If thereading device determines that a particular assay result should bedisregarded it may prompt the user to repeat the assay.

Any device which is compatible for use with an assay test strip,preferably a reflectance reader, for determining the assay result iscontemplated for use herein. Such test strip devices as are known tothose of skill in the art (see, e.g., U.S. Pat. Nos. 5,658,801,5,656,502, 5,591,645, 5,500,375, 5,252,459, 5,132,097). Reflectance andother readers, including densitometers and transmittance readers, areknown to those of skill in the art (see, e.g., U.S. Pat. Nos. 5,598,007,5,132,097, 5,094,955, 4,267,261, 5,118,183, 5,661,563, 4,647,544,4,197,088, 4,666,309, 5,457,313, 3,905,767, 5,198,369, 4,400,353).

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. (canceled)
 2. A process for capturing images from a diagnostic testor assay at a low capture rate, the process comprising: receiving afirst synchronizing signal from an image sensor in signal communicationwith the at least one microprocessor, the image sensor configured tostore data indicative of a video frame, the first synchronizing signalindicating at least whether the image sensor is storing data indicativeof an end of a video frame; receiving a second synchronizing signal fromthe image sensor, the second synchronizing signal indicating at leastwhether the image sensor is storing data indicative of an end of one ofa plurality of lines of the video frame; receiving a clock signal fromthe image sensor, the clock signal indicating whether the image sensoris currently storing valid data indicative of at least a portion of thevideo frame; at a first point in time, determining: whether the firstsynchronizing signal indicates that the image sensor is storing dataindicative of the end of at least the portion of the video frame, andwhether the second synchronizing signal indicates that the image sensoris storing data indicative of the end of one of the plurality of linesof the video frame; and in response to determining both that the firstsynchronizing signal indicates that the image sensor is storing dataindicative of the end of the video frame and that the secondsynchronizing signal indicates that the image sensor is storing dataindicative of the end of one of the plurality of lines of the videoframe: polling the clock signal until the clock signal indicates thatthe image sensor is currently storing valid data indicative of at leasta portion of the video frame, and when the clock signal indicates thatthe image sensor is currently storing valid data indicative of at leasta portion of the video frame, reading and storing the then-stored dataindicative of at least the portion of the video frame from the imagesensor during a current data-valid half-period, the video framerepresenting an outcome of the diagnostic test or assay.
 3. The processof claim 2, further comprising polling the clock signal until the clocksignal indicates that the image sensor is currently storing valid dataindicative of at least a portion of the video frame.
 4. The process ofclaim 3, further comprising: detecting at least one of a rising edge ofthe clock signal and falling edge of the clock signal; and determining,based on the detected rising edge or falling edge, that the image sensoris currently storing valid data indicative of at least a portion of thevideo frame.
 5. The process of claim 2, further comprising storing, viaa general purpose input/output peripheral or an external memory, thethen-stored data indicative of at least the portion of the video framefrom the image sensor.
 6. The process of claim 2, wherein the process isrepeated a number of times.
 7. A process for capturing images from adiagnostic test or assay at a low capture rate, the process comprising:receiving a first synchronizing signal from an image sensor in signalcommunication with the at least one microprocessor, the image sensorconfigured to store data indicative of a video frame, the firstsynchronizing signal indicating at least whether the image sensor isstoring data indicative of an end of a video frame; receiving a secondsynchronizing signal from the image sensor, the second synchronizingsignal indicating at least whether the image sensor is storing dataindicative of an end of one of a plurality of lines of the video frame;receiving a clock signal from the image sensor, the clock signalindicating whether the image sensor is currently storing valid dataindicative of at least a portion of the video frame; detecting aninterrupt based on the clock signal, the interrupt indicating that theimage sensor is currently storing valid data indicative of at least aportion of the video frame; upon detection of the interrupt: determiningwhether the first synchronizing signal indicates that the image sensoris storing data indicative of the end of the video frame, anddetermining whether the second synchronizing signal indicates that theimage sensor is storing data indicative of the end of one of theplurality of lines of the video frame; and in response to determiningthat both the first synchronizing signal indicates that the image sensoris storing data indicative of the end of the video frame and the secondsynchronizing signal indicates that the image sensor is storing dataindicative of the end of one of the plurality of lines of the videoframe, reading and storing the then-stored data indicative of the videoframe from the image sensor during a current data-valid half-period, thevideo frame representing an outcome of the diagnostic test or assay. 8.The process of claim 7, further comprising detecting the interrupt basedon the clock signal by determining a feature of the clock signal,wherein the feature is one of a rising edge and a falling edge of theclock signal.
 9. The process of claim 7, further comprising storing, viaa general purpose input/output peripheral, the then-stored dataindicative of at least the portion of the video frame from the imagesensor.
 10. The process of claim 7, further comprising storing, via anexternal memory interface, the then-stored data indicative of at leastthe portion of the video frame from the image sensor.
 11. The process ofclaim 7, wherein the process is repeated a number of times.
 12. Aprocess for capturing images from a diagnostic test or assay at a lowcapture rate, the process comprising: receiving a first synchronizingsignal from an image sensor in signal communication with the at leastone microprocessor, the image sensor configured to store data indicativeof a video frame, the first synchronizing signal indicating at leastwhether the image sensor is storing data indicative of an end of a videoframe; receiving a clock signal from the image sensor, the clock signalindicating whether the image sensor is currently storing valid dataindicative of at least a portion of the video frame; detecting aninterrupt based on the first synchronizing signal, the interruptindicating that the image sensor is storing data indicative of the endof one of the plurality of lines of the video frame; and in response todetecting the interrupt: determining whether the image sensor iscurrently storing valid data indicative of at least the portion of thevideo frame, and in response to determining that the image sensor iscurrently storing valid data indicative of at least the portion of thevideo frame, reading and storing the then-stored data indicative of atleast the portion of the video frame from the image sensor during acurrent data-valid half-period, the video frame representing an outcomeof the diagnostic test or assay.
 13. The process of claim 12, furthercomprising detecting the interrupt based on the clock signal bydetermining a feature of the clock signal, wherein the feature is one ofa rising edge and a falling edge of the first synchronizing signal. 14.The process of claim 12, further comprising: polling the clock signal todetermine a data-valid edge of the clock signal; and determining, basedon the determined data-valid edge, that the image sensor is currentlystoring valid data indicative of at least the portion of the videoframe.
 15. The process of claim 14, wherein the data-valid edge of theclock signal comprises one of a rising edge of the clock signal and afalling edge of the clock signal.
 16. The process of claim 12, furthercomprising, in response to determining that the image sensor iscurrently storing valid data indicative of the video frame, reading thethen-stored data indicative of the video frame from the image sensorwithin a time period equal to less than one-half of the period of theclock signal.
 17. The process of claim 12, further comprisingdetermining whether the image sensor is currently storing valid dataindicative of the video frame based on whether the clock signal iscurrently in a data-valid half-period.
 18. The process of claim 17,further comprising, in response to determining that the image sensor iscurrently storing valid data indicative of the video frame: reading thethen-stored data indicative of the video frame only during the currentdata-valid half-period, and reading and storing the then-stored dataindicative of the video within a full period of the clock signal. 19.The process of claim 12, wherein the process is repeated a number oftimes.
 20. A process for capturing images from a diagnostic test orassay at a low capture rate, the process comprising: receiving a firstsynchronizing signal from an image sensor in signal communication withthe at least one microprocessor, the image sensor configured to storedata indicative of a video frame, the first synchronizing signalindicating at least whether the image sensor is storing data indicativeof an end of one of a plurality of lines of the video frame, receiving aclock signal from the image sensor, the clock signal indicating whetherthe image sensor is currently storing valid data indicative of at leasta portion of the video frame, detecting an interrupt based on the firstsynchronizing signal, the interrupt indicating that the image sensor isstoring data indicative of the end of one of the plurality of lines ofthe video frame, and in response to detecting the interrupt: reading thethen-stored data indicative of at least the portion of the video framefrom the image sensor only during the current data-valid half-period dueto an alignment of the execution of the instructions with the clocksignal, and storing the then-stored data indicative of at least theportion of the video frame, during a current data-valid half-period, thevideo frame representing an outcome of the diagnostic test or assay. 21.The process of claim 20, wherein the process is repeated a number oftimes.